Thailand has faced its most severe political crisis in almost 20 years, as supporters of former Prime Minister Thaksin Shinawatra have mounted an increasing challenge through anti-government protests seeking to topple the Democrat-led government of Prime Minister Abhisit Vejjajiva.

During the two-month anti-government protests, 90 people were killed, both civilian and military, and nearly 1,900 people were injured.

Many protesters came from rural backgrounds, the key political base for Mr. Thaksin, who was ousted by a 2006 coup. He had been accused largely by the urban middle class of corruption and abuse of power.

Some foreign media have reported the protests as being between the rural poor and urban middle class.

But Indian-born economist and Nobel laureate Amartya Sen says calling the crisis 'class warfare' is an 'oversimplification' of the problem.

"To describe the whole thing as a class war between the rich and poor of a very complex problem - I could not begin to take that as a good way of describing it," he said. "While I was skeptical of basically the foreign news coverage, the BBC as well as CNN and it also includes the New York Times, I have to say that I knew well enough both about Thailand and about conflict in general to regard this to be hardly a possible explanation, to say it is class war."

Prime Minister Abhisit has established several commissions to investigate the bloodshed and also seek ways of promoting political reforms. But the Thai military is resisting calls for a complete lifting of a state of emergency that remains in several provinces, including the capital, Bangkok.

Tuesday, the military said political activities of the opposition Puea Thai Party and Red Shirt supporters still constituted a 'threat'. The military expressed its concerns before a weekend by-election in an outer constituency of Bangkok.

The vote is the first major political test since the military ended the protests in May. The opposition candidate - a former Red Shirt leader - remains behind bars to face charges for his role in the anti-government protests.

Public opinion polls put the governing candidate ahead of the opposition. But newspaper editorials have been critical of the opposition candidate's continuing detention, amid reports of threatened censorship of his campaign video speeches.